C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  template class with template as parameter          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Mehturt@gmail.com Guest Posted: Tue Nov 29, 2005 4:06 pm    Post subject: template class with template as parameter I have this code which compiles fine under gcc 4: #include <vector> #include <string> template< typename T = std::string , template , typename stringize_operation = stringize_fo<T> Quote: class Stringizer { // member functions here }; However, when compiling using cxx (Compaq C++ V6.5-014 for Compaq Tru64 UNIX V5.1B (Rev. 2650)) I get the following errors: cxx: Warning: ***.hh, line 55: declaration of "T" hides template parameter , template <typename T> class CONTAINER = std::vector -------------------------------------^ cxx: Error: ***.hh, line 56: class template "std::vector" is not compatible with template template parameter "CONTAINER" , typename stringize_operation = stringize_fo<T> ----------------^ I wonder whether gcc or cxx is correct. Thanks [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Carl Barron Guest Posted: Wed Nov 30, 2005 10:56 am    Post subject: Re: template class with template as parameter In article <1133276845.346304.247910 (AT) o13g2000cwo (DOT) googlegroups.com>, <"Mehturt (AT) gmail (DOT) com"> wrote: Quote: I have this code which compiles fine under gcc 4: #include <vector #include template typename T = std::string , template , typename stringize_operation = stringize_fo<T class Stringizer { // member functions here }; However, when compiling using cxx (Compaq C++ V6.5-014 for Compaq Tru64 UNIX V5.1B (Rev. 2650)) I get the following errors: cxx: Warning: ***.hh, line 55: declaration of "T" hides template parameter , template -------------------------------------^ cxx: Error: ***.hh, line 56: class template "std::vector" is not compatible with template template parameter "CONTAINER" , typename stringize_operation = stringize_fo<T ----------------^ I wonder whether gcc or cxx is correct. Thanks the template std::vector has two parameters not one and gcc is in error in extending this. This a major problem with template template parameters. either pass the complete container type as a type parameter or require two parameters of the template template parameter. [template class vector;] template < class C =std::vector class Op = stringize_to<typename C::value_type> Quote: class Stringizer { public: typedef typename C::value_type T; // ... }; is probably the 'best' solution, as it will work with any class C having member functions of std::vector you use in Stringizer, with the same semantics as those of std::vector and has a member typedef value_type, the type stored in the container. More compilers than not will behave as cxx. Technically gcc is non-standard here. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ Language (Moderated) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.